A diesel engine, similar to many other types of engines, is primarily cooled through a liquid coolant system wherein water, or anti-freeze, or a mixture thereof passes between a radiator and various components of the engine needing heat dissipation.. A plurality of coolant conduits and a coolant pump are provided to communicate the coolant and power the system, respectively. One area of a diesel engine directly cooled by such a coolant system is the engine block. Specifically, the actual cylinders within the engine block are subjected to extreme temperatures during the combustion of the diesel fuel and need constant cooling.
Modern heavy duty diesel engines used in large trucks and off highway equipment typically include cylinder liners which occupy the inside of the cylinders, and are made of replaceable cast iron to facilitate easy replacement and rebuilding of the diesel engine, as opposed to light duty engines which require the entire cylinder head to be replaced. The coolant can be directed from the pump to the outside surface of the cylinder liner to dissipate heat. Seals are provided at the top and bottom of the cylinder liner to prevent leakage of coolant into the cylinders.
One problem associated with cylinder liners, is that they vibrate as the engine operates. Specifically, the reciprocating motion of the pistons and the pressure of combustion causes the liners to move back and forth within the cylinders. As this vibration continues over time, vapor bubbles are formed in the coolant due to the liner movement away from the coolant. When the piston reverses direction, the liner moves against the coolant and causes the vapor bubbles to implode. This constant scouring action eventually erodes the liner and can potentially allow coolant to enter the cylinder and engine lubrication system. This phenomenon is known as cavitation erosion or liner pitting. In certain instances, such cavitation erosion can occur in as few as 250 hours or 12,000 miles of operation for the diesel engine. This consequently results in an extreme expense to the operator of the engine.
With typical diesel engines, the water or anti-freeze is periodically filtered to prevent contaminants from reaching and potentially damaging the various moving components of the diesel engine. More recently, diesel engines have been designed to include supplemental coolant additives which are added to the water or the anti-freeze to perform additional functions within the engine such as minimizing cavitation erosion and corrosion.
Systems have therefore been designed which release a chemical additive into the water or anti-freeze which counteracts the effects of such vibration and dramatically reduces the occurence of cavitation erosion. Such supplemental coolant additives, or SCAs normally include a chemical combination including nitrites such as borate and nitrite, or molybdate, phosphate and nitrite, which chemically react with the water or anti-freeze (ethylene or propylene glycol) to produce a coating on the outside of the cylinder liners which discourages cavitation erosion.
Since a relatively small amount of SCA is required within the coolant, systems have been devised to slowly release the chemical additive into the water or coolant stream over time to elongate the productive life of the SCA supply. Normally, the SCA chemicals are added to the water in conjunction with a coolant filter provided adjacent the water pump of the diesel engine.
However, as diesel engine manufacturers are requiring longer and longer intervals between the changing of filters, current SCA release mechanisms do not provide a sufficiently long life to allow the changing of the coolant filter to correspond with the changing of the fuel and oil filters of the diesel engine. Moreover, current systems often allow for an inaccurately regulated amount of SCA to be released into the coolant stream, or allow relatively large particles of SCA to be released therein and thereby potentially damage the diesel engine. Furthermore, current methods of manufacturing coolant filters and systems for releasing chemical additives into the coolant stream have resulted in fairly cost prohibitive systems in that complicated devices are provided to allow for the delayed release of the chemical additives into the coolant stream, while at the same time providing the mechanism by which the coolant stream can be filtered.